The present invention relates to a propulsion system for a vehicle.
Hybrid vehicles may be powered by a primary prime mover which may be a combustion engine, and by a secondary prime mover which may be an electrical machine. The electrical machine will be equipped with at least one battery to store electrical energy and with regulating equipment to regulate the flow of electrical energy between the battery and the electrical machine. The electrical machine may thus serve alternately as motor and generator, depending on the vehicle's operating state. When the vehicle is braked, the electrical machine generates electrical energy which is stored in the battery. The stored electrical energy is subsequently used to operate the vehicle. The electrical machine may be situated at a location between a clutch mechanism and the gearbox of the vehicle. For the sake of space, it is advantageous to connect the electrical machine directly to the input shaft of the gearbox.
There are disadvantages in using a conventional clutch mechanism which disconnects the gearbox input shaft from the engine during gearchange processes in the gearbox. When a vehicle moves off from stationary, the discs of the clutch mechanism slide against one another, thereby warming them. This warming results in greater fuel consumption and in clutch disc wear. A conventional clutch mechanism is also relatively heavy and expensive. It also occupies a relatively large amount of space in the vehicle.
U.S. Pat. No. 6,354,974 refers to a propulsion system for a hybrid vehicle provided with a combustion engine and an electrical machine which is situated on the output shaft of the engine. The object is to create a compact propulsion unit which need not use a conventional clutch mechanism. The conventional clutch mechanism is replaced by a planetary gear and three friction clutches. The friction clutches make it possible to create various operating states of the vehicle. Using friction clutches results in energy losses.